Microelectromechanical Systems (MEMS) stand poised for the next major breakthrough in the silicon revolution that began with the transistor in the 1960s and has revolutionized microelectronics. MEMS allow one to not only observe and process information of all types from small scale systems, but also to affect changes in systems and the environment at that scale. “RF MEMS Switches and Integrated Switching Circuits” builds on the extensive body of literature that exists in research papers on analytical and numerical modeling and design based on RF MEMS switches and micromachined switching circuits, and presents a unified framework of coverage. This volume includes, but is not limited to, RF MEMS approaches, developments from RF MEMS switches to RF switching circuits, and MEMS switch components in circuit systems. This book also: -Presents RF Switches and switching circuit MEMS devices in a unified framework covering all aspects of engineering innovation, design, modeling, fabrication, control and experimental implementation -Discusses RF switch devices in detail, with both system and component-level circuit integration using micro- and nano-fabrication techniques -Includes an emphasis on design innovation and experimental relevance rather than basic electromagnetic theory and device physics “RF MEMS Switches and Integrated Switching Circuits” is perfect for engineers, researchers and students working in the fields of MEMS, circuits and systems and RFs.

Ultrasmall Radio Frequency and Micro-wave Microelectromechanical systems (RF MEMs), such as switches, varactors, and phase shifters, exhibit nearly zero power consumption or loss. For this reason, they are being developed intensively by corporations worldwide for use in telecommunications equipment. This book acquaints readers with the basics of RF MEMs and describes how to design practical circuits and devices with them. The author, an acknowledged expert in the field, presents a range of real-world applications and shares many valuable tricks of the trade.

In order to incorporate the RF MEMS technology with the 3D MMICs technology, a novel RF MEMS switch was designed and implemented in a 3D MMIC circuit environment. RF MEMS switches possess many advantages compared to traditional solid-state switches, such as high electromechanical isolation, and ultra-low power consumption. The novelty of this switch was that it was based on low temperature processing techniques. Design equations for a shielded coplanar waveguide were derived for the switch. Traditional lumped element capacitor model and this newly developed distributed transmission line models were compared against measured data to verify their validity. While measurement results show good agreement with both models, the distributed model consistently demonstrated better match than its lumped element counterpart. Test and measurement results showed that a typical RF MEMS switch was capable of delivering less than 0.2dB insertion loss and more than 14.1dB isolation between input and output ports at X-band (8GHz-12GHz). This RF MEMS switch required only 12V actuation voltage while it was capable of handling 2.88W RF power before "hot-switching" occurs. Hysteretic phenomenon of RF MEMS switches was observed; release voltage threshold was found to be around 2V 4V, much lower than the one required for pulling down the structure. Switching speeds of RF MEMS switches with different beam strength were measured using a novel experimental setup utilizing couplers as bias networks. The fastest switches demonstrated maximum switching speed of 3.571 kHz and more than 10,800,000 life cycles. As the application of RF MEMS switches, a 4-bit digital phase shifter was designed and fabricated. 180ʻ bit and 90ʻ bits were realized using reflection type phase shifters, while the 45ʻ and 22.5ʻ bits were achieved using loaded-line type phase shifters. A novel reflection type phase shifter loaded with multiple switch pairs was developed and was capable of delivering multiple phase shift angles within one circuit stage. Phase shifter measurement results were consistent with simulated results.

This dissertation presents designs, fabrication processes and measurements of a series of high performance RF MEMS switches. Chapter 2 presents a miniature RF MEMS metal contact switch based on a tethered-cantilever structure. The miniature size and the use of tethers result in an excellent biaxial residual stress and stress gradient tolerance. The switch is built using thin metal process with a large biaxial stress and a high stress gradient (50 MPa and -105 MPa/um), and works well under these conditions. In the up-state, the switch capacitance is 9.4 fF and results in an isolation of 20 dB at 20 GHz. In the down-state, the switch resistance is 3.6 ohm for a gold-gold contact under 30 V actuation voltage. The switch is compatible with CMOS back-end processing. With its miniature size, the switch could be placed in arrays to achieve lower contact resistance and higher power handling. Chapter 3 presents a multi-contact mN-force RF MEMS metal-contact switch with a pull-down voltage (Vp) of 45 V-50 V and an operation voltage of 60V-65V. The switch gets a contact force of s 2.0 mN under 65 V actuation voltage and a release force of s 1.2 mN (simulated). The switch gets an on-state resistance of s 1.8 with Ru-Au contact and an off-state capacitance of 13.5 fF, which results in a figure of merit of 24 fs. In the temperature stability measurement, the switch shows a change of 4V in pull-down voltage and a change of 2V in release voltage from 25 C to 125 C. In the high power handling measurement, the switch demonstrates a reliability of > 10 million cold switching cycles with 5 W RF power. Chapter 4 first presents a high capacitance ratio (Cr) capacitive switch with continuous tuning capability after pull-down. The measured up-state capacitance is 74 fF. The pull-down voltage of the switch is 30V -32V and there is an 8.4% linear tuning range from 33V to 40V actuation voltage. The measured down-state capacitance is 1296 fF under 40V actuation voltage, resulting in a Cr of 17.5. Next, a back-to-back switch using the high Cr switch is designed to improve IP2 without extra power supply. The back-to-back switch shows an up-state capacitance of 31fF, a Cr of 19.7 and a 6.8% continuous tuning range from 34V to 40V. The back-to-back switch shows a 14 dB higher OIP2 than the single switch does.